### Span Identifiers
###
###

use std::type;
use std::binary;
use std::array;
use std::string;

## Is the `span_id` valid
##
## Checks the `span_id` argument to see if it is a valid
## span id. A legal span id is one of:
##
## * An array of integers in the range of [0..=255] of length 8
## * A binary 8 byte value
## * An array of 8 int values
## * A 16-byte hex-encoded string
## * Regardless of representation, the value must not be all zeroes
##
## Returns a record when the representation is well-formed of the form:
##
## > ```tremor
## > {
## >    "kind": "string"|"binary"|"array", # Depends on input
## >    "valid": true|false,               # True if well-formed and valid
## >    "value": "<span_id>"               # Representation depends on `kind`
## > }
## > ```
##
## Returns an empty record `{}` when the representation not well-formed
##
fn is_valid(span_id) of
    # String representation
    case(span_id) when type::is_string(span_id) =>
      { "string": span_id != "0000000000000000" and string::bytes(span_id) == 16, "value": span_id }
    # Binary representation
    case(span_id) when type::is_binary(span_id) =>
      let arr = binary::into_bytes(span_id);
      { "binary": array::len(arr) == 8 and span_id != << 0:64 >>, "value": span_id }
    # Array representation
    case(span_id) when type::is_array(span_id) =>
      { "array": array::len(arr) == 8 and span_id != [ 0, 0, 0, 0, 0, 0, 0, 0], "value": span_id }
    case _ =>
      {}
end